Free lean calculators
Eight calculators for common lean and Six Sigma measures: OEE, takt time, kanban cards, flow efficiency, Little's Law, control charts, sigma level and process capability. Each one shows its formula, a worked example and what the result means.
OEE Calculator
Overall equipment effectiveness shows how much of your planned production time was productive. Enter one shift's numbers to see availability, performance, quality and the loss that costs you most.
Use it when: you want to know where a machine or line loses productive time.
Availability × Performance × Quality
Open calculatorTakt Time Calculator
Takt time is the pace a lean process has to keep: the time available divided by what the customer needs. Enter your shift pattern and daily demand, and add your total work content to see how many operators the line needs.
Use it when: you need the pace a line must run at to meet demand.
Available time ÷ Customer demand
Open calculatorLittle's Law Calculator
Little's Law links three flow metrics: work in progress, throughput and cycle time. Enter any two and the calculator finds the third, then shows what happens to cycle time if you cut work in progress.
Use it when: you want to see how work in progress drives lead time.
Cycle time = WIP ÷ Throughput
Open calculatorSix Sigma Calculator
This Six Sigma calculator turns defect counts into the standard Six Sigma measures: sigma level, DPMO and yield. Enter the units you inspected, the opportunities for a defect on each unit and the defects you found.
Use it when: you need defects per million and a sigma level from defect counts.
DPMO → yield → sigma level
Open calculatorProcess Capability Calculator
This process capability calculator works out the process capability ratio Cp and the index Cpk, which show whether a stable process fits inside its specification limits. Enter the lower and upper spec limits, the process mean and the standard deviation.
Use it when: you need to know whether a stable process fits inside its spec limits.
(USL − LSL) ÷ 6σ
Open calculatorControl Chart Calculator
This control chart calculator builds an individuals and moving range (I-MR) chart from your measurements. Paste readings in time order to get the center line, upper and lower control limits, and a flag on any point outside them.
Use it when: you want to know whether a process is stable or something unusual happened.
x̄ ± 2.66 × MR̄
Open calculatorFlow Efficiency Calculator
This flow efficiency calculator shows how much of a process's lead time is spent working on the item and how much is spent waiting. Enter the work time at each step and the wait that follows it, as you would read them off a value stream map.
Use it when: you have mapped a process and want to see how much of the lead time is waiting.
Value-added time ÷ Lead time
Open calculatorKanban Calculator
This kanban calculator works out how many kanban cards, and so how many containers, a pull loop needs. Enter average daily demand, the replenishment lead time, a safety factor and the quantity in each container.
Use it when: you are setting up a card or bin kanban loop and need the card count.
D × L × (1 + S) ÷ C
Open calculatorFor vendors
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